witness

noun

1.
someone who sees an event and reports what happened
informant witnesser
Derived from:
witness
2.
a close observer; someone who looks at something (such as an exhibition of some kind)
umbloater looker spectator viewer watcher
Derived from:
witness
3.
testimony by word or deed to your religious faith
witness for Christ
4.
(law) a person who attests to the genuineness of a document or signature by adding their own signature
attestant attestator attestor
Derived from:
witness
5.
(law) a person who testifies under oath in a court of law
Derived from:
witness